The present invention relates to a blue-color light-emitting aluminate phosphor and a fluorescent lamp using the same.
Recently, demand has arisen for general illumination fluorescent lamps having high output and high color-rendering properties. This demand is met by three-band type fluorescent lamps wherein blue, green, and red phosphors, having emission spectrum distributions of relatively narrow wavelength ranges, are mixed in an appropriate mixing ratio.
A recent three-band type fluorescent lamp uses an aluminate phosphor as a blue-color light-emitting component. However, a europium-activated aluminate phosphor [(Ba,Eu)Mg.sub.2 Al.sub.16 O.sub.27 ] (Japanese Patent Publication (Kokoku) No. 52-22836) as a known blue phosphor is not satisfactory, since its emission intensity descreases during use. Other europium-activated aluminate phosphors [(Ba,Eu)O.eAl.sub.2 O.sub.3.fy.sub.2 O.sub.3 ] (Japanese Patent Disclosure (Kokai) No. 60-139784) and [Ba.sub.1-g-h Sr.sub.g Mg.sub.i.Al.sub.j O.sub.1+i+j/2 :Eu.sub.h.sup.2+ ] (Japanese Patent Disclosure (Kokai) No. 56-86982) are also not satisfactory since their emission intensities are low and decrease during use.
The emission colors of the respective phosphors of these types of fluorescent lamp differ greatly. When the emission outputs (emission inensities) of the respective phosphors decrease while the lamp is in use, color deviation occurs, degrading the color rendering properties.
Japanese Patent Disclosure (Kokai) No. 57-207678 discloses a fluorescent lamp having a combination of 3(M,Eu).sub.3 (PO.sub.4).sub.2.m'Cl.sub.2 or k(M.sub.1-o Eu.sub.o O).lP.sub.2 O.sub.5 mM'X.sub.2.nB.sub.2 O.sub.8 as a blue phosphor, (Re.sub.1-p-q-r Tb.sub.p Ce.sub.q As.sub.r).sub.2 O.sub.3 .mu.SiO.sub.2..nu.P.sub.2 O.sub.5 as a green phosphor, and (Y,Eu).sub.2 O.sub.3 as a red phosphor. With this lamp, however, color deviation occurs during use, due to a difference in the degradation rates of the respective phosphors, thus a decrease in the total luminous flux intensity of the lamp is large.